Eccentric flexural pivot

ABSTRACT

A flexural pivot device having first and second housing means arranged on a common axis and being axially spaced from each other, the first housing means having an inwardly projecting arcuate structure disposed eccentric to the common axis, the arcuate structure extending axially into the second housing means and being radially spaced therefrom, a second housing means having inwardly projecting arcuate structure disposed eccentric to the common axis and being diametrically disposed relative to the arcuate structure of the first housing means, the arcuate structure of the second housing means extending axially into said first housing means and being radially spaced therefrom, and cross flat spring means connecting said arcuate structures so that said first and second housing means are rotatable relative to each other on the common axis.

United States Patent 1 Troeger May 28, 1974 1 i ECCENTRIC FLEXURAL PIVOT[75] inventor: Henry Troeger, Cooperstown, NY.

[73] Assignee: The Bendix Corporation, Teterboro,

[22] Filed: Sept. 8, 1972 [2]] Appl. No.: 287,299

Primary Examiner-James B. Marbert Attorney, Agent, or FirmAnthony Cuoco;S. H. Hartz [57] ABSTRACT A flexural pivot device having first andsecond housing means arranged on a common axis and being axially spacedfrom each other, the first housing means having an inwardly projectingarcuate structure disposed eccentric to the common axis, the arcuatestructure extending axially into the second housing means and beingradially spaced therefrom, a second housing means having inwardlyprojecting arcuate structure disposed eccentric to the common axis andbeing diametrically disposed relative to the arcuate structure of thefirst housing means, the arcuate structure of the second housing meansextending axially into said first housing means and being radiallyspaced therefrom, and cross flat spring means connecting said arcuatestructures so that said first and second housing means are rotatablerelative to each other on the common axis.

5 Claims, 4 Drawing Figures Pmimiummzss I974 3.8111089 sum 1 or 2 I IFIGURE I PAIENIEUIIAY 28 I974 SHEET 2 OF 2 FIGURE 4 FIGURE 3 FIGURE 2ECCENTRIC FLEXURAL PIVOT FIELD OF THE INVENTION This invention relatesto devices for supporting a mechanism which is to be limitedly rotatedabout an axis and more particularly concerns improvements in fiexuralpivot devices which provide limited relative rotation between two partsby flexing flat springs connecting the two parts.

CROSS REFERENCE TO RELATED CASES This patent application is related tomy commonly assigned co-pending patent application U.S. Ser. No.287,298, filed Sept. 8, 1972.

DESCRIPTION OF THE PRIOR ART Prior art fiexural pivot devices such asthose disclosed in my commonly assigned US. Pat. No. 3,181,851 discloseda pivot which was more economical to produce than its predecessordesigns. In particular, this patent disclosed a pivot comprised of apair of flat crossed springs assembled to two pair of arcuate quadrantelements, two of which were slotted and alternately disposed, bonded asa unit and then with the outer sleeve means cut to form a fiexuralpivot. Although the basic resilient core design was unique, it requiredfour quadrant members which had to be stamped and accurately coined, thesprings and quadrants had to be assembled and unitized such as bybonding, two diametrically opposed reliefs had to be ground on the CD.of the core, an outer sleeve had to be mounted to the core assembly andthen this assembly had to be unitized, a circumferential groove had tobe cut therein and the two ends had to be cut and discarded. Thus, thispivot design required essentially five parts and fifteen individual andbatch operations.

A subsequent fiexural pivot device disclosed in thecommonly assigned US.Pat. No. 3,319,951 issued in the name of Frederick A. Seelig, eliminatedthe steps of under-cutting the CD. of the core and the step of cuttingthe ends of both core and support structure, however, this device stillrequired the basic core and the problems associated therewith as wasmentioned above. Also, the support structure called for in this patentwas relatively expensive to form.

My commonly assigned co-pending patent application Ser. No. 286,367disclosed a method of making a fiexural pivot having few parts andgreatly reducing the number of operations to be performed inconstructing the device. However, the particular electrode designdisclosed therein was expensive to fabricate and did not resolve inuniform electrical machining since fresh electrolytic or dielectricfluid could not easily be introduced between the electrode and sleevebecause the electrode could not be rotated during the machiningoperation.

SUMMARY OF THE INVENTION centric to the common axis, the arcuatestructure ex-.

tending axially into said second housing means and being radially spacedtherefrom, the second housing means having inwardly projecting arcuatestructure disposed eccentric to the common axis and being diametricallydisposed relative to the arcuate structure of the first housing means,the arcuate structure of the second housing means extending axially intothe first housing means and being radially spaced therefrom, and a pairof crossed flat springs interconnecting the arcuate structures so thatthe first and second housing means are rotatable relative to each otheron the common axis.

It is, therefore, a primary object of this invention to provide afiexural pivot which requires fewer parts, fewer manufacturingoperations, less materialand results in stronger pivots than previousdevices.

Another object of the present invention is to provide an improvedfiexural pivot device which is simply constructed and can be made insmall sizes and which retains the advantages of no backlash and nofriction or wear with resulting limitations due to lubrication at hightemperature.

A further object of the present invention is to provide an improvedfiexural pivot device which has axially aligned housing membersconnected by a structure including crossed flat springs whereby thedevice can be simply mounted in support structure and can provide afriction-free sensitive pivotable mounting suitable for high temperatureapplications.

Further objects of this invention are to simplify the method ofmanufacture of fiexural pivots, to make flexural pivots from only threeparts, to reduce the amount of scrap material produced in themanufacture of flexural pivots, to reduce the cost of manufacture offlexural pivots, and to improve the performance characteristics offiexural pivots.

Still a further object of this invention is to provide a fiexural pivothaving internal axially extending arcuate structure formed eccentric tothe axis of rotation, the eccentric disposition of the arcuate structurepermitting the pivot to be manufactured with a hollow mill or by use ofa cylindrical electrode in an electro-chemical or electrical dischargemachining operation. Such an electrode design permits the use of simpletubular electrodes which are more economical to make, can be easilyfabricated from a variety of materials-suitable for electrodes, e.g.,graphite, and can be rotated so that fresh electrolytic or dielectricfluid will be introduced between the electrode and sleeve thus washingout the debris resulting from electrical machining. The last mentionedcondition being very important since it permits uniform electricalmachining and low electrode wear.

The invention further lies in the particular organization of the variouselements and their cooperative association with one another to producethe beneficial results intended. The foregoing objects and advantages ofthe invention will appear more fully hereafter from the consideration ofthe description which follows, taken together with the accompanyingdrawings wherein the preferred embodiment of the invention isillustrated. It is to be expressly understood, however, thatthe drawingsare for the purpose of illustration and description and notto beconstrued as defining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective viewillustrating from left to right a broken-away view of the pivot housingafter forming the eccentric arcuate structure, a view of a typicalelectrode that can be utilized in forming the eccentric arcuatestructure and the subassembly of the flat crossed springs.

FIG. 2 is a longitudinal cross-section of a pivot according to myinvention taken along the section 2--2 of FIG. 3.

FIG. 3 is an end view of the pivot shown in FIG. 2.

FIG. 4 is a transverse cross-sectional view of my pivot taken along thesection lines 44 of FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, the mainhousing of my pivot is shown as a cylindrical member having fourdiametrically opposed slots 12 therein. Housing 10 can be cast or formedfrom common bar stock and the slots 12 can be formed by broaching,milling or other conventional means. Two flat springs 21 and 22 arestamped or chemical milled from resilient stock and are assembled asshown. I-shaped spring 22 is slipped through insertion opening 25 in thesquare-D-shaped spring 21 and the cross element 27 is arrangedperpendicular to cross bars 29 and 31 of the square-D-shaped spring 21.Spring 21 has between its cross bars 29 and 31 an axially-extendingprojection 35. I-shaped spring 22 also has projections 37. It is to benoted that the crossed bars 29 and 31 and cross element 27 merge on aradius to the various projections whereby the cross spring elements arebetter supported and more durable under flexing when bonded to thehousing as will be described. It is apparent that two generally I-shapedsprings can be used provided the effective width is about equal, as withthe total width of the two bars 29 and 31 relative to the cross element27. The various projections, of course, have the same thickness as thecross members since the springs are made from metal sheet. Although onlyone type of flexural arrangement is shown, it should be noted that amyriad of alternate designs could also be used with departing from myinvention. For example, a plurality of flat, rectangular flexures or thelike as disclosed in my commonly assigned US. Pat. No. 3,073,584 couldalso be successfully employed.

Housing 10 is placed in a machine capable of removing metal byelectrochemical or electrical discharge means. Cylindrical electrodes15, having an OD. less than the CD. of housing 10, and an ID. greaterthan the ID. of housing 10 (although this latter condition is not aprerequisite), are advanced into housing 10 on an axis parallel to theaxis of housing 10 and displaced from the axis of housing 10 at adistance less than that which would allow the electrode to break throughthe external surface of housing 10. This process is performed atdiametrically opposed ends of housing 10 at an axial depth sufficient toform overlapping arcuate structures 50 and 60 displaced 180 from eachother. The arcuate structures thus formed are eccentric to the axis ofhousing 10 having equally spaced axially extending edges and beingradially spaced from housing 10 at each end thereof.

The subassembly comprised of the resilient members 21 and 22 and/or thesleeve or housing 10 are plated with metals capable of forming a brazedattachment of flexures to the housing 10. The subassembly is theninserted into housing 10 with the projections 37 and 35 of the resilientmembers mating with the slots 12 of the housing. The assembly of theflexures in the housing can easily be accomplished with automatedequipment. The assembly of housing and flexures are then brazedtogether, preferably by heating in a controlled nonoxidizing atmosphereat a temperature suitable for providing both brazing and proper heattreatment for best flexure properties. Other means of attaching theflex-- ures to the sleeve such as by bonding or welding may also beused, although these means usually require the use of holding fixturesand the like.

Referring to FIG. 2, a circumferential groove is cut into housing 10 asby grinding or other conventional means so that it extends into or belowthe annular arcuate spaces 32 and 34 formed by the electrodes 15. Twoslots 36 (only one shown) are cut, as by broaching or grinding duringthe same operation immediately above, in housing 10 so as to extendbelow and therefore sever the inner cusps 38 formed by the inner surfaceof groove 30 and the outer surfaces of the annular arcuate spaces 32 and34 shown in FIG. 4. These operations result in separating the sleeve orhousing into two cylindrical members 55 and 65 having inwardlyprojecting arcuate structures 50 and 60, respectively, joined only bythe flexures 21 and 22 which maintain axial coincidence of the housingportions 55 and 65 but because of the flexures ability to bend thehousing portions 55 and 65 may be rotated with respect to each otherthrough some angle limited by bending stresses in the flexures. Althoughthe flexures of the preferred embodiment of a pivot made according to myinvention are shown substantially perpendicular to each other, oneskilled in the art will appreciate that in some cases an unequal angularspacing of the flexures may be desirable.

It should be noted that the objects and advantages of my invention areaccomplished and in particular that the cylindrical annular spaces 32and 34 may be formed with a hollow mill or by the electromechanical orelectrical discharge machining as was described. The cylindrical formpermits the use of simple tubular electrodes 15 which are economical tomake, can be fabricated from a variety of materials suitable forelectrodes, for example graphite, and can be rotated so that freshelectrolytic or dielectric fluid will be introduced between theelectrode and housing thus washing out the debris resulting from theelectrical machining. Obviously, this last condition is very importantfor uniform electrical machining and low electrode wear.

The operation of the flexural pivot device shown in FIG. 2 as a pivotalmounting is believed to be apparent from the foregoing description.Thus, with reference to FIG. 6 an instrument indicator, one end of abutterfly valve, a turbine engine control vane, one end of a flightvehicle control surface or many other devices which are usually mountedin bearings and have limited rotation or pivoting is mounted to thefirst housing means 55 and the second housing means 65 is mounted in ahole and support structure and fixed by a set pin or other conventionalarrangement. When the instrument indicator, for example, is actuated ina clockwise direction, the first housing means 55 is rotated clockwisefrom the normal position with the flexing of the springs 21 and 22 as iswell known in flexural pivot devices. The radial spacing between theaxially extending eccentric arcuate structures 50 and 60, one endillustrated in FIG. 3, provide clearance upon the flexing or bending ofthe springs 21 and 22. Rotation can be made in either direction aslimited by the resistance of the flexures toward radial or axial forces.It is to be noted that the present easily replaceable flexural pivot ismade from only three parts, a cylindrical housing and two flat crossedsprings, which are connected by a single bonding step and is morecompact for a given capacity then constructions which have springsconnected by screws to nontubular mounting means, etc.

It is also to be understood that changes can be made in the disclosedembodiment and methods by persons skilled in the art without departingfrom the scope of the invention as set forth in the appended claims.

I claim:

1. A flexural pivot device comprising:

first and second housing means arranged on a common axis and axiallyspaced from each other;

said first housing means having an inwardly projecting arcuate structureeccentric to said common axis, said arcuate structure extending axiallyinto said second housing means and being radially spaced therefrom;

said second housing means having inwardly projecting arcuate structureeccentric to said common axis and being diametrically disposed relativeto said arcuate structure of said first housing means, said arcuatestructure of said second housing means extending axially into said firsthousing means and being radially spaced therefrom; and

crossed flat spring means connecting said arcuate structures so thatsaid first and second housing means are rotatable relative to each otheron said common axis.

2. A flexural pivot comprised of:

a pair of flat crossed springs, each of said crossed springs having atleast one side projection at each end, each said side projectionextending perpendicularly from the side end of the spring and being thesame thickness as said spring to provide connecting segments;

first and second arcuate elements disposed eccentric to the axis formedby the crossed springs, said first and second arcuate elementsdiagonally opposed and fixedly secured to said connecting segments toprovide a tubular assembly having two semicircular-like membersinterconnected by crossed fiat springs and spaced at the lengthwiseedges thereof;

first outer sleeve means connected to one of said semi-circular-likemembers and radially spaced from the other member; and

second outer sleeve means connected to the other of saidsemi-circular-like members and radially spaced from the first member,whereby said first outer sleeve means can be fixed and said second outersleeve means can be rotated with flexing of said crossed springs.

3. A flexural pivot device comprised of first and second arcuateelements arranged eccentric to a common circle with adjacent axial edgesequally spaced;

crossed flat springs connecting said arcuate elements and providing anaxis of relative rotation for said elements coincident with said commoncircle; first means for mounting a rotatable member connected to saidfirst element and being free of any connection to said second element;and second means for providing a fixed support connected to said secondelement and being free of any connection to said first element. 4. Acantilever-type flexural pivot device comprised of:

first and second cylindrical means arranged on a common axis and axiallyspaced from each other;

said first cylindrical means having inwardly thereof arcuate structure,said arcuate structure extending axially into said second cylindricalmeans and being eccentric to and radially spaced therefrom;

said second cylindrical means having inwardly thereof arcuate structurediametrical of said arcuate structure of said first cylindrical means,said arcuate structure of said second cylindrical means extendingaxially into said first cylindrical means and being eccentric to andradially spaced therefrom;-

crossed flat spring means connecting said arcuate structures so thatsaid first and second cylindrical means are rotatable relative to eachother on'said common axis,,said spring means being so constructed as tolimit relative rotation between said cylindrical means;

said first cylindrical means including a first tubular member adapted toprovide a fixed end support; and

said second cylindrical means including a second tubular member adaptedto provide a rotatable mounting.

5. A flexural pivot device comprised of first and second arcuate innersleeve elements arranged eccentric to a common circle with axiallyextending edges being equally spaced and disposed from each other;

first and second outer sleeve means arranged on an axis coincident withsaid common circle, said first and second outer sleeve means beingformed integral with said first and second inner sleeve elementsrespectively;

said first inner sleeve element being radially spaced from said secondouter sleeve means; said second inner sleeve element being radiallyspaced from said first outer sleeve means; and resilient means mountedinternally of said inner sleeve elements whereby said first outer sleevemeans can be fixed and said second outer sleeve means can be rotated byflexing said resilient means;

1. A flexural pivot device comprising: first and second housing meansarranged on a common axis and axially spaced from each other; said firsthousing means having an inwardly projecting arcuate structure eccentricto said common axis, said arcuate structure extending axially into saidsecond housing means and being radially spaced therefrom; said secondhousing means having inwardly projecting arcuate structure eccentric tosaid common axis and being diametrically disposed relative to saidarcuate structure of said first housing means, said arcuate structure ofsaid second housing means extending axially into said first housingmeans and being radially spaced therefrom; and crossed flat spring meansconnecting said arcuate structures sO that said first and second housingmeans are rotatable relative to each other on said common axis.
 2. Aflexural pivot comprised of: a pair of flat crossed springs, each ofsaid crossed springs having at least one side projection at each end,each said side projection extending perpendicularly from the side end ofthe spring and being the same thickness as said spring to provideconnecting segments; first and second arcuate elements disposedeccentric to the axis formed by the crossed springs, said first andsecond arcuate elements diagonally opposed and fixedly secured to saidconnecting segments to provide a tubular assembly having twosemi-circular-like members interconnected by crossed flat springs andspaced at the lengthwise edges thereof; first outer sleeve meansconnected to one of said semi-circular-like members and radially spacedfrom the other member; and second outer sleeve means connected to theother of said semi-circular-like members and radially spaced from thefirst member, whereby said first outer sleeve means can be fixed andsaid second outer sleeve means can be rotated with flexing of saidcrossed springs.
 3. A flexural pivot device comprised of first andsecond arcuate elements arranged eccentric to a common circle withadjacent axial edges equally spaced; crossed flat springs connectingsaid arcuate elements and providing an axis of relative rotation forsaid elements coincident with said common circle; first means formounting a rotatable member connected to said first element and beingfree of any connection to said second element; and second means forproviding a fixed support connected to said second element and beingfree of any connection to said first element.
 4. A cantilever-typeflexural pivot device comprised of: first and second cylindrical meansarranged on a common axis and axially spaced from each other; said firstcylindrical means having inwardly thereof arcuate structure, saidarcuate structure extending axially into said second cylindrical meansand being eccentric to and radially spaced therefrom; said secondcylindrical means having inwardly thereof arcuate structure diametricalof said arcuate structure of said first cylindrical means, said arcuatestructure of said second cylindrical means extending axially into saidfirst cylindrical means and being eccentric to and radially spacedtherefrom; crossed flat spring means connecting said arcuate structuresso that said first and second cylindrical means are rotatable relativeto each other on said common axis, said spring means being soconstructed as to limit relative rotation between said cylindricalmeans; said first cylindrical means including a first tubular memberadapted to provide a fixed end support; and said second cylindricalmeans including a second tubular member adapted to provide a rotatablemounting.
 5. A flexural pivot device comprised of first and secondarcuate inner sleeve elements arranged eccentric to a common circle withaxially extending edges being equally spaced and disposed 180* from eachother; first and second outer sleeve means arranged on an axiscoincident with said common circle, said first and second outer sleevemeans being formed integral with said first and second inner sleeveelements respectively; said first inner sleeve element being radiallyspaced from said second outer sleeve means; said second inner sleeveelement being radially spaced from said first outer sleeve means; andresilient means mounted internally of said inner sleeve elements wherebysaid first outer sleeve means can be fixed and said second outer sleevemeans can be rotated by flexing said resilient means.